Dual control valve assembly

ABSTRACT

A simplified dual control valve assembly for operating a pair of hydraulic jacks in unison, each control valve being operable to selectively communicate operating pressure to one end of each jack, separate pumps providing fluid under pressure to each of the control valves through inlet conduits which are in communication with each other by means of a restrictive orifice. The restrictive orifice assures balanced fluid pressures available to both of the control valves while pressure equilizing lines effectively communicate respective portions of the hydraulic jacks to assure their operation in unison.

United States Patent 91 eck et ai.

[ Nov. 12, 1974 DUAL CONTROL VALVE ASSEMBLY [75] Inventors: Henry E. Beck, Oswego; Wayne A.

Peterson, Joliet, both of I11.

[73] Assignee: Caterpillar Tractor Co., Peoria, Ill.

[22] Filed: Sept. 4, 1973 [21] Appl. No.: 394,192

[52] US. Cl. 91/413, 91/461 [51] Int. Cl FlSb 11/22 [58] Field of Search 91/411 8,411 R,4l3, 461; 60/97 E [56] References Cited UNITED STATES PATENTS I 1,900,050 3/1933 Ernst 60/97 E 2,449,269 9/1948 Austin 9l/4l3 X 3,295,420 l/l967 Cryder et al. 9l/4ll R Primary Examiner-Edgar W. Geoghegan Attorney, Agent, or FirmPhillips, Moore, Weissenberger, Lempio & Strabala [57] ABSTRACT A simplified dual control valve assembly for operating a pair of hydraulic jacks in unison, each control valve being operable to selectively communicate operating pressure to one end of each jack, separate pumps providing fluid under pressure to each of the control valves through inlet conduits which are in communica tion with each other by means of a restrictive orifice. The restrictive orifice assures balanced fluid pressures available to both of the control valves while pressure equilizing lines effectively communicate respective portions of the hydraulic jacks to assure their operation in unison.

8 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION The present invention relates to a hydraulic control circuit wherein two hydraulic jacks are operated in unison by a pair of control valves. More particularly, the invention contemplates a simplified arrangement of the valves to facilitate their interconnection with the two jacks.

Hydraulic jacks are commonly employed in pairs to operate various material handling or earthmoving implements, for example. In such arrangements, the two jacks retract and extend in unison. However, for other applications such as where two hydraulic jacks are employed for steering, they may operate in unison but in opposition to each other, one jack retracting and the other jack extending at the same time, for example. The present invention is particularly described below with reference to an application where the jacks extend and retract in unison. However, it will be obvious that the control circuit of the present invention is adapted to jacks which operate in opposition to each other as well.

Due to hydraulic flow requirements in such machinery, it is also common to provide a separate control valve and pump for regulating each of the hydraulic jacks. Such a system is disclosed in US. Pat. No. 3,486,418 to Cryder et al, that patent being assigned to the assignee of the present invention while further disclosing the use of cross lines between jacks to insure equal operating pressures within such a system.

Within such arrangements, paired control valves may be arranged in parallel relation or as part of a bank of control valves. Due to the number of control valves commonly required and also due to the size of interconnecting hoses and other components, such hydraulic control circuits tend to become relatively complex and difficult to assemble.

SUMMARY OF THE INVENTION duits which are in communication with each other through a restrictive orifice to assure a supply of operating fluid at substantially equal pressures to the control valves.

Additional objects and advantages of the present invention are made apparent in the following description having reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation, with parts in section, of a hydraulic control circuit including two hydraulic control valves for simultaneously operating two hydraulic jacks.

FIG. 2 is a fragmentary view with parts in section, showing the two hydraulic jacks arranged in parallel with a preferred arrangement of the two control valves 2 therebetween to facilitate their interconnection with the two jacks.

FIG. 3 is an enlarged fragmentary view illustratingin greater detail the access conduits for interconnecting the two control valves with the two jacks.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a hydraulic control circuit of the type contemplated by the present invention is indicated at 11 for simultaneously operating a pair of hydraulic jacks l2 and 13. Generally, the control circuit 11 includes two pilot operated control valves 14 and 16 which are operable in unison by a pilot control valve indicated at 17. Pilot fluid is supplied to the valve 17 from a pump 18 with the pilot fluid pressure being extablished by a relief valve 19.

Pumps 21 and 22 are in respective communication with the two control valves through conduits 23 and 24. Relief valves 26 and 27 are respectively associated with the two pumps to regulate their output pressures. Through this arrangement, fluid for the valve 14 is sub stantially provided by the pump 21 while fluid for the valve 16 is substantially provided by the pump 22. A restrictive orifice 28 interconnects the inlet conduits 23 and 24 in order to assure that equal fluid pressures are delivered to the two control valves.

The control valve 14 has an inlet port 31 for receiving fluid from the conduit 23. The inlet port 31 is in communication with a branched supply conduit 32 by means of an inlet check valve 33. The valve 14 also includes a pair of service ports or chambers 34 and 36 spaced apart on opposite sides of branched conduit 32 with drain ports 37 and 38 being arranged respectively adjacent the service ports. A valve spool 39 is slidably arranged within a bore 41 to selectively regulate communication of the service ports 34 and 36 with either the branched supply conduit 32 or the drain ports 37 and 38. The valve spool 39 is shown in a neutral position under the influence of a centering spring mechanism 42 where both of the service chambers 34 and 36 are blocked from communication with either the supply passage 32 or the drain ports 37 and 38. Makeup valves 43 and 44 respectively provide communication between the service ports 34, 36 and the drain ports 37, 38 whenever fluid pressure in one of the service ports is less than the fluid pressure in the drain passages. This of course is a conventional arrangement to prevent cavitation within the jacks 12 and 13.

The other valve 16 similarly includes an inlet port 51 I communicating the conduit 24 with a branched supply conduit 52 across an inlet check valve 53. The valve 16 similarly includes service ports or chambers 54 and 56 with associated drain ports 57 and 58. A valve spool 59 is slidably positioned within a bore 61 under the influence of a centering spring mechanism 62. Makeup valves 63 and 64 similarly provide selective communication of the service ports 54 and 56 with the drain ports 57 and 58 for the purpose of preventing cavitation within the jacks l2 and 13. The spool 59 of the control valve 16 is also shown in a neutral position under the influence of the centering spring 62 so that both service ports 54 and 56 are blocked from fluid' communication with either the branched supply conduit 52 or the drain ports 57, 58.

The spools 39 and 59 of the parallel control valves 14 and 16 are operable in opposition to each other in response to pilot fluid pressure communicated to the valves through branched pilot conduits 66 and 67. With pilot fluid pressure introduced into the branched conduit 66, the spool 39 is shifted rightwardly as viewed in FIG. 1 to communicate the service port 34 with the branched supply conduit 32 and to communicate the service port 36 with the drain port 38. The spool 59 is simultaneously shifted to the left to communicate the service port 54 with the branched supply conduit 52 and to communicate the service port 56 with the drain port 58. Note that the pressurized service ports 34 and 54 are respectively communicated with the rod ends of the jacks 12 and 13 respectively by means of access conduits 68 and 69. Similarly, the service ports 36 and 56 are communicated with the head ends of the hydraulic jacks l3 and 12 respectively by means of access conduits 71 and 72. Because of the crossover relation of the access conduits 69 and 71 (this feature being better illustrated in FlGS. 2 and 3), the jacks 12 and 13 are simultaneously urged into retraction. Exhaust fluid from the head ends of the jacks is communicated to drain through the access conduits 71 and 72.

When the pilot control valve 17 is positioned to communicate pilot fluid pressure through the conduit 67, the spools 39 and 59 are shifted in respectively opposite directions so that fluid under pressure is communicated to the head ends of the jacks 12 and 13 through the conduits 72 and 71. Fluid pressure from the rod ends of the jacks is then communicated to drain through the conduits 68 and 69.

This arrangement of the two control valves 14 and 16 together with the manner of interconnecting the valves with the jacks l2 and 13 permits a simplified arrange- -ment of access conduits as is more clearly illustrated in FIGS. 2 and 3. As was noted above, the conduits 69 and 71 are arranged in cross-over relation to achieve simultaneous extension and retraction of the jacks 12 and 13. However, for certain applications the cross-over arrangements could be eliminated so that the jacks 12 and 13 would then simultaneously operate in opposition to each other.

Additional features of the present invention further facilitate the association of the control valves with the hydraulic jacks while assuring balanced operating pressures therefor. For example, it was noted above that the restrictive orifice 28 assures substantially equal inlet pressures for the control valves 14 and 16. To further insure equal pressurization of the hydraulic jacks 12 and 13,an equalizing conduit 73 is arranged in communication between the service ports 34 and 54 while a similar equalizing conduit 74 communicates the service ports 36 and 56. These conduits assure equal pressurization in the head ends and rod ends respectively of the two jacks 12 and 13.

Additionally, a common drain manifold 76 is provided for common relief flow from the drain ports 37, 38 of the valve 14 and drain ports 57, 58 of the valve 16. The common drain manifold 76 is also in communication with additional drain ports 77 and .78 in the valves 14 and 16 respectively. When the spools 39 and 59 are in their centered positions as illustrated in FIG. 1, the fluid from the inlet conduits 23 and 24 is communicated to the common drain manifold 76 therethrough. The common drain manifold permits more compact arrangement of the valves 14 and 16 as is illustrated in FIGS. 2 and 3.

Referring briefly to FIGS. 2 and 3, it may be seen that the preferred arrangement of the valves 14 and 16 substantially simplifies interconnection of the valves with the jacks l2 and 13. For example, each of the access conduits 68, 69, and 71, 72 includes a U-shaped portion communicating one of the service ports (see FIG. 1) with interconnecting conduits 68A, 69A and 71A, 72A. The opposite ends of these interconnecting conduits are then placed in communication with appropriate ends of the jacks l2 and 13.

We claim:

1. A hydraulic control circuit for operating a pair of double-acting hydraulic jacks in unison, each of the jacks having a rod end and a head end, the hydraulic control circuit comprising two similar control valves responsive to a common actuating means, each control valve including a fluid inlet port, two service chambers and drain means, a spool being movable within each control valve by the common actuating means for selectively communicating the service chambers with the inlet port and drain means, each control valve having its service chambers in communication with one end of each of the two hydraulic jacks,

two similar sources of fluid under pressure,

inlet conduit means respectively communicating the two sources with the fluid inlet ports for the two control valves, and

means defining a restrictive orifice arranged in communication between the two inlet conduits.

2. The control circuit of claim 1 wherein the two control valves are pilot operated and the common actuating means is a pilot control circuit including a pilot control valve.

3. The hydraulic control circuit of claim 2 wherein the pilot actuated control valves are arranged in parallel relation with each other, the pilot actuated spools being simultaneously operable in opposition to each other, the service chambers on adjacent ends of the two control valves being in respective communication with opposite ends of the same hydraulic jack.

4. The control circuit of claim 3 further comprising pressure equalizing conduits respectively communicating with service chambers in the two control valves for balancing operating pressure communicated to the two hydraulic jacks.

5. The hydraulic control circuit of claim 4 further comprising a common drain manifold arranged between the two control valves, the common drain manifold being in communication with the drain means of each control valve, each control valve having a neutral position wherein the service chambers are blocked by the spool, the spool in each control valve including means for communicating the respective fluid inlet port with the common drain manifold when the control valve is in its neutral condition.

6. The hydraulic control circuit of claim 5 wherein the two hydraulic jacks are mounted in parallel relation for extending and retracting operation, the two control valves being arranged in parallel relation with each other and in transverse relation with the hydraulic jacks, a pair of access conduits communicating the service chambers of each valve with the respective hydraulic jacks, each access conduit including a U-shapctl conduit portion.

7. The hydraulic control circuit of claim 6 wherein the U-shaped conduit portion for one of the control 6 valves is arranged in cross-over relation to permit simunication with service chambers in the two control iP l f retractlon and extenslon of the two hydrau' valves for balancing operating pressures simultaneously 1c ac s.

8. The control circuit of claim 1 further comprising commumcated to the two hydrauhc Jackspressure equalizing conduits each in respective com- 5 

1. A hydraulic control circuit for operating a pair of doubleacting hydraulic jacks in unison, each of the jacks having a rod end and a head end, the hydraulic control circuit comprising two similar control valves responsive to a common actuating means, each control valve including a fluid inlet port, two service chambers and drain means, a spool being movable within each control valve by the common actuating means for selectively communicating the servicE chambers with the inlet port and drain means, each control valve having its service chambers in communication with one end of each of the two hydraulic jacks, two similar sources of fluid under pressure, inlet conduit means respectively communicating the two sources with the fluid inlet ports for the two control valves, and means defining a restrictive orifice arranged in communication between the two inlet conduits.
 2. The control circuit of claim 1 wherein the two control valves are pilot operated and the common actuating means is a pilot control circuit including a pilot control valve.
 3. The hydraulic control circuit of claim 2 wherein the pilot actuated control valves are arranged in parallel relation with each other, the pilot actuated spools being simultaneously operable in opposition to each other, the service chambers on adjacent ends of the two control valves being in respective communication with opposite ends of the same hydraulic jack.
 4. The control circuit of claim 3 further comprising pressure equalizing conduits respectively communicating with service chambers in the two control valves for balancing operating pressure communicated to the two hydraulic jacks.
 5. The hydraulic control circuit of claim 4 further comprising a common drain manifold arranged between the two control valves, the common drain manifold being in communication with the drain means of each control valve, each control valve having a neutral position wherein the service chambers are blocked by the spool, the spool in each control valve including means for communicating the respective fluid inlet port with the common drain manifold when the control valve is in its neutral condition.
 6. The hydraulic control circuit of claim 5 wherein the two hydraulic jacks are mounted in parallel relation for extending and retracting operation, the two control valves being arranged in parallel relation with each other and in transverse relation with the hydraulic jacks, a pair of access conduits communicating the service chambers of each valve with the respective hydraulic jacks, each access conduit including a U-shaped conduit portion.
 7. The hydraulic control circuit of claim 6 wherein the U-shaped conduit portion for one of the control valves is arranged in cross-over relation to permit simultaneous retraction and extension of the two hydraulic jacks.
 8. The control circuit of claim 1 further comprising pressure equalizing conduits each in respective communication with service chambers in the two control valves for balancing operating pressures simultaneously communicated to the two hydraulic jacks. 